You do need to make contact with the hospital surgery team and let them know and just get it checked out. They should have informed the patient of what to expect in the first few days after surgery. You could also contact the GP if this is easier to do. You can also ring NHS 111 for medical advice out of hours as well.
It is likely to be debris and dried blood clots that collects in the throat after the surgery itself, and this will clear. It is best to expel it gently. Sipping fluids regularly will help.
